1. Field of the Invention
The present invention relates in general to a tamper-evident container closure and container neck structure in which the closure is applied to the neck with an axial downward force. The closure is removed by unscrewing it from the neck. The tamper-evident skirt of the closure ruptures when the closure is initially removed from the container neck. The absence of the tamper-evident skirt provides visible evidence that the container has been opened and the contents of the container possibly tampered with by a dishonest patron.
The present invention further relates to a closure thread structure in which the threads are interrupted, in one modification having a vertical gap between adjacent ends of thread segments and in another modification having staggered thread segments and staggered gaps between segments. In a still further modification there is a vertical space between thread segments which accommodates a foil seal tear tab. The present invention further relates to a PET neck structure wherein the edges of the ratchet teeth are rounded.
2. Description of the Prior Art
The fewer the number of threads on a container neck, the easier is axial application--i.e., downward application of force on the cap which fits on the neck. However, fine threads require increased aggregate linear thread engagement for security, since the radial thread engagement achieved is reduced. Excessive aggregate linear thread engagement on threads having few leads requires excessive turning to remove and re-apply the cap. Therefore, a combination of fine threads having many leads has been taught in the art. Angelo Guala SpA UK Pat. Application GB 2144553 and Massmould Holdings, Ltd. European Patent Specification 0 118 267 each show six leads. U.S. Pat. Nos. 5,307,946 and 5,560,504, show seven threads. U.S. Pat. No. 5,553,727 discloses ten threads.
U.S. Pat. No. 5,593,055 discloses many features of construction of the container neck and cap hereinafter described. This reference discloses seven leads.
U.S. Pat. No. 5,480,045 illustrates a form of horizontal tear tab used in one modification of this invention.
U.S. Pat. No. 5,664,694 illustrates a vertical space formed by interrupting cap skirt threads to accommodate the tab used to remove foil disks sealing container neck lips.